One of the key maintenance activities in a solar power plant deploying parabolic reflectors is frequent washing of surface of the parabolic reflectors to remove the dust collected on the surface of the parabolic reflector. Three types of water washing techniques have been are reported in literature for washing the surface of the parabolic reflectors. The techniques include high volume pressure water spray, low volume high pressure spray and mechanical scrubbing along with water wash.
These processes are mostly automated, for example, some power plants use a movable arm to spray pressurized jet of water onto the surface of the parabolic reflector. In certain aspects, robotic systems can also be deployed. It is stated that automation is economical if the frequency of cleaning is less than a fortnight. Cleaning frequency varies based on period of the year (e.g. more in summer months). However, there is no guarantee whether the cleaning interval is optimum. Due to cost involved in cleaning the entire field at regular intervals and associated water consumption (some plants even use demineralized water), it is useful to identify a method to know if the parabolic reflectors require cleaning.
Automated methods to identify cleaning intervals for a power plant do not exist currently. There are some instruments based on optical techniques (scattering) that are available as a handheld device for flat mirrors, (e.g. heliostats) only. These instruments cannot however be used for parabolic mirrors due to their focusing geometry.
Conventional systems for monitoring parabolic reflectors require the use of ground systems with alignment fixtures. Thus for a solar thermal field alignment fixtures are required to be positioned at every parabolic reflector. Additionally, ground based systems required increased manual intervention.